Physicochemical and morphological properties of spin-coated poly(3-alkylthiophene) thin films

Poly(3-hexylthiophene) (P3HT) and poly(3-octylthiophene) (P3OT) were synthesized by direct oxidation of the respective monomers with FeCl3 as oxidant/catalyst. It was observed that the type of monomer affected the molecular weight and polydispersity as well as degree of regioregularity of the polymer, measured by size exclusion chromatography and by 1H nuclear magnetic resonance, respectively. Homogeneous P3HT and P3OT films were prepared by spin-coating technique with different polymer concentration in solutions. Morphology study with atomic force microscopy indicates the cluster size difference between P3HT and P3OT films. Optical absorption properties of the polymeric films were analyzed in pristine and doped state. The electrochemical characterization of the poly(3-alquilthiophenes) (P3Ats) films showed two oxidation peaks, one at 0.35 V vs. Ag/AgCl, and the second one at 0.8 V vs. Ag/AgCl. The colors of the film at these two potentials were black and blue, respectively.